ars,
however, astronomers have unexpectedly and recently been more fortunate
than with Sirius, and have been able to calculate their distances from
the earth. The celebrated BESSEL, and soon afterwards, the late Mr.
HENDERSON, astronomer royal for Scotland, were the first to surmount the
difficulty that had baffled the telescopic resources of the HERSCHELS.
BESSEL detected a parallax of one-third of a second in the star 61
Cygni, and in the constellation of the Centaur HENDERSON found another
star whose parallax amounted to one second. Of the million of fixed
glittering points that adorn the sky, these are the only two whose
distances have been calculated, and to express them, miles, leagues, or
orbits seems inadequate. Light, whose speed is known to be 192,000 miles
per second, would be three years in reaching our earth from the star of
HENDERSON; and starting from BESSEL'S star and moving at the same rate
it could only reach us in ten years. These are the nearest stars, but
there are others whose distances are immeasurably greater, and whose
light, though starting from them at the beginning of creation, may not
have reached our globe!

The stars visible to the eye are about 3,000, but the number increases
with every increase of telescopic power, and may be said to be
innumerable. They are not of uniform lustre or form, but vary in figure
and brightness. Some of them have a _nebulous_ or cloudy appearance; and
there are entire clusters with this dusky aspect, mostly pervaded,
however, with luminous points of more brilliant hue. In the outer fields
of astral space Sir WILLIAM HERSCHEL observed a multitude of nebulae, one
or two of which may be seen by the naked eye. All of them, when seen by
instruments of low power, look like masses of luminous vapour; but some
of them had brighter spots, suggesting to Sir WILLIAM the idea of a
condensation of the nebulous matter round one or more centres. But when
these luminous masses are examined by more powerful instruments many of
them lose their cloudy form, and are resolved into shining points, "like
spangles of diamond dust." It is in this way several nebulae have yielded
to the gigantic reflector of Lord ROSSE, and others with still greater
optical resources may follow. This brings us to the first questionable
and controversial portion of the _Vestiges_; namely,--the

NEBULAR HYPOTHESIS.

It is among the gaseous bodies just described, in the outer boundary of
Nature, whic